Pulsed HV vacuum breakdown of polished, powder coated, and E-beam treated large area stainless steel electrodes with 0.5 to 7 mm Gaps

Johnson, D. J.; Savage, M. E.; Sharpe, R.A.; Batrakov, A. V.; Proskurovsky, D.I.

doi:10.1109/tdei.2006.1593401

Cited by 26 publications

(4 citation statements)

References 30 publications

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“…However, some of our observations combined with recent measurements by others bring this into question. Johnson, et al, has observed a breakdown dependence consistent with the total voltage effect with slightly longer, 160 ns pulses, and a similar experimental setup [4]. They also measured large breakdown fields at the smallest gaps, much larger than we usually assume in high-power cross-field devices, as shown in Fig.…”

Section: Introductionsupporting

confidence: 83%

Pulsed vacuum breakdown measurements with a 1-MV generator

Allen¹,

Hinshelwood²,

Schumer³

et al. 2015

2015 IEEE Pulsed Power Conference (PPC)

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Measurements of the breakdown field of vacuum gaps have been made with a 1-MV, 50-ns test stand [1]. The first set of experiments was performed with planar, bare metal electrodes [2]. This geometry had an enhanced anode edge that affected measurements. Here, we report on a new set of measurements using anodes without field enhancement. Diagnostics include current and voltage probes, x-ray detector, x-ray pinhole camera and a fast framing camera. The results of these measurements give new insight into the cause of anode interactions that reduce the breakdown field with large gaps.

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Section: Introductionsupporting

confidence: 83%

Pulsed vacuum breakdown measurements with a 1-MV generator

Allen¹,

Hinshelwood²,

Schumer³

et al. 2015

2015 IEEE Pulsed Power Conference (PPC)

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“…However when there is a hole in the bottom electrode this Hall-driven axial flow can occur unimpeded. It was in such an experiment that the unexpected axial asymmetry in radiated power was first identified [406]. This process is the basis of a plasma opening switch.…”

Section: Axial Asymmetries and Flows; Radial Electric Fieldsmentioning

confidence: 98%

“…It was interpreted that when E r is positive the electrons are driven into the wire core and there is more energy deposition leading to a conical core expansion. A negative electric field would lead to electron field emission when E r exceeds 300 kV cm −1 [406], followed by vapour breakdown. Then a current shunt to the plasma forms around the wire requiring a lower voltage to drive the current.…”

Section: Axial Asymmetries and Flows; Radial Electric Fieldsmentioning

confidence: 99%

A review of the denseZ-pinch

Haines

2011

Plasma Phys. Control. Fusion

391

184

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The Z-pinch, perhaps the oldest subject in plasma physics, has achieved a remarkable renaissance in recent years, following a few decades of neglect due to its basically unstable MHD character. Using wire arrays, a significant transition at high wire number led to a great improvement in both compression and uniformity of the Z-pinch. Resulting from this the Z-accelerator at Sandia at 20 MA in 100 ns has produced a powerful, short pulse, soft x-ray source >230 TW for 4.5 ns) at a high efficiency of ∼15%. This has applications to inertial confinement fusion. Several hohlraum designs have been tested. The vacuum hohlraum has demonstrated the control of symmetry of irradiation on a capsule, while the dynamic hohlraum at a higher radiation temperature of 230 eV has compressed a capsule from 2 mm to 0.8 mm diameter with a neutron yield >3 × 10 11 thermal DD neutrons, a record for any capsule implosion. World record ion temperatures of >200 keV have recently been measured in a stainless-steel plasma designed for Kα emission at stagnation, due, it was predicted, to ion-viscous heating associated with the dissipation of fast-growing short wavelength nonlinear MHD instabilities. Direct fusion experiments using deuterium gas-puffs have yielded 3.9×10 13 neutrons with only 5% asymmetry, suggesting for the first time a mainly thermal source. The physics of wire-array implosions is a dominant theme. It is concerned with the transformation of wires to liquid-vapour expanding cores; then the generation of a surrounding plasma corona which carries most of the current, with inward flowing low magnetic Reynolds number jets correlated with axial instabilities on each wire; later an almost constant velocity, snowplough-like implosion occurs during which gaps appear in the cores, leading to stagnation on the axis, and the production of the main soft-x-ray pulse. These studies have been pursued also with smaller facilities in other laboratories around the world. At Imperial College, conical and radial wire arrays have led to highly collimated tungsten plasma jets with a Mach number of >20, allowing laboratory astrophysics experiments to be undertaken. These highlights will be underpinned in this review with the basic physics of Z-pinches including stability, kinetic effects, and finally its applications.

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“…Johnson et al investigated the vacuum breakdown sustained by 160 ns voltage pulses. Results showed that breakdown field was ~1300 kV cm −1 for 80 mm diameter polished stainless-steel electrodes, and 15% lower than that for 120 mm polished and e-beam treated electrodes [26]. Descoeudres et al compared the DC breakdown conditions for different metals under ultrahigh vacuum [27].…”

Section: Introductionmentioning

confidence: 99%

Effect of cathode and anode materials on the high-energy electron beam in the nanosecond-pulse breakdown in gas-filled diodes

Zhang¹,

Huang²,

Ding³

et al. 2019

J. Phys. D: Appl. Phys.

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High-energy electron beam can be generated during the breakdown process in a gas diode at elevated pressures. The design of electrodes in the gas diode affects the parameters of these electron beams. In this paper, investigation on parameters of the runaway electron beam (REB) in air and nitrogen excited by nanosecond pulsed generators are presented. Experiments were carried out with gas diodes by using cathode and anode made of different materials, including stainless steel, aluminum, copper and titanium. Experimental results show that, in the case of nanosecond-pulse breakdown, the cathode material significantly affects the amplitude of the REB current pulse when either pressure or gap spacing are small. When the pressure is low, the REB current is highest for the stainless steel cathode due to its small electron work function. However, the REB current for the aluminum, copper and titanium cathodes is higher than that of stainless steel cathode at atmospheric pressure because of the Malter effect on their surfaces. The dependence of the amplitude of the REB current on the anode foils is investigated by using aluminum, titanium, copper and tantalum. The experimental results show that the atomic number of the metal, as well as mass mean free path of the electron in it contribute to the amplitude of the REB current pulse. Based on the REB currents of different anode foils, energy distribution of runaway electrons is estimated. Electron distribution with an average energy of ~55 keV is obtained when the amplitude of the applied voltage pulse across the discharge gap is 110 kV. The results may contribute to the design of the gas diode for the generation of high-energy electron beams in nanosecond-pulse breakdown.

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Pulsed HV vacuum breakdown of polished, powder coated, and E-beam treated large area stainless steel electrodes with 0.5 to 7 mm Gaps

Cited by 26 publications

References 30 publications

Pulsed vacuum breakdown measurements with a 1-MV generator

Pulsed vacuum breakdown measurements with a 1-MV generator

A review of the denseZ-pinch

Effect of cathode and anode materials on the high-energy electron beam in the nanosecond-pulse breakdown in gas-filled diodes

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